Holly S. Shulman

Computational Modeling and Experimental Microwave Processing of JSC-1A Lunar Simulant

AbstractMicrowave heating is a potential method for mitigating dust issues and creating solid regolith structures, such as landing pads, on the moon, Mars, and other extraterrestrial bodies. The advantage of using microwave heating is that regolith has the potential to be directly heated in situ. A computational model was developed that predicts the heating behavior of a lunar simulant, JSC-1A, using various methods for applying microwave energy. The efficiency of microwave heating depends on the properties of the materials. Dielectric properties are used to characterize a material’s microwave behavior, which is temperature and frequency dependent. Obtaining a variety of actual regolith samples for dielectric characterization can be challenging, which is why simulants and computational models were developed. This work used lunar simulant JSC-1A for dielectric characterization, microwave-processing studies, and computational modeling, inasmuch as this simulant is available in large quantities and has been ...

High-Temperature Microwave Dielectric Properties and Processing of JSC-1AC Lunar Simulant

AbstractSuccessful development of extraterrestrial microwave heating technologies depends on the study of the dielectric properties that control the microwave heating behavior of simulants and regoliths. Microwave heating may serve many lunar applications including heating the regolith for lunar surface dust stabilization, oxygen production, building materials, and mineral refinement. The dielectric properties (dielectric constant, e′, and loss factor, e″) of the lunar simulant, JSC-1AC, were measured at 2.45 GHz microwave frequency from room temperature to 1,100°C. The dielectric loss tangent and half-power depth were calculated from the measured properties. The loss tangent increased from a low value of 0.02 at room temperature to a high value of 0.31 at 1,100°C, indicating increased efficiency of microwave absorption at higher temperatures. The low temperature loss tangent indicated that relatively slow, low efficiency heating would be expected at room temperature. The microwave heating experiments con...

Modeling of hybrid (heat radiation and microwave) high temperature processing of limestone

Incorporation of radiant boundary conditions is proposed for multiphysics (electromagnetic and thermal) modeling to cover practically valuable scenarios of hybrid (heat radiation and microwave) thermal processing of materials. The algorithm is implemented by making the models of radiation in ANSYS Fluent available for the electromagnetic models in QuickWave-3D. The resulting simulator is applied to the process of hybrid heating of cylindrical samples of limestone in Ceralinks MATTM kiln. Time-temperature history of the heating process is simulated along with the temperature field. Hybrid heating is shown to be more efficient in terms of heating rate and tempera-ture uniformity.

Microwave Enhanced Direct Cracking of Hydrocarbon Feedstock for Energy Efficient Production of Ethylene and Propylene.

This project demonstrated microwave cracking of ethane with good product conversion and ethylene selectivity, with a short residence time ({approx}0.001 sec). The laboratory scale equipment was designed and built, along with concept designs for larger scale implementation. The system was operated below atmospheric pressures, in the range of 15-55 torr, with argon as a carrier gas. The measured products included hydrogen, methane, acetylene, and ethylene. The results followed similar trends to those predicted by the modeling software SPYRO{reg_sign}, with the exception that the microwave appeared to produce slightly lower amounts of ethylene and methane, although enhanced analytical analysis should reduce the difference. Continued testing will be required to verify these results and quantify the energy consumption of microwave vs. conventional. The microwave cracking process is an attractive option due to the possibility of selectively heating the reaction volume rather than the reactor walls, which may allow novel reactor designs that result in more efficient production of ethylene. Supplemental studies are needed to continue the laboratory testing and refine processing parameters.